1. Field of the Invention
The present invention relates to a method and apparatus for removing from a granular material at least one substance capable of being burned. More specifically, the present invention is concerned with a method and apparatus for regenerating granular desiccative material rendered ineffective by at least one contaminant.
2. Brief Description of the Prior Art
As well known to those of ordinary skill in the art, granular desiccative material (desiccants) are used in many applications for absorbing moisture. With time, desiccants become contaminated by water, oil or any other substance to which they are exposed. When they are saturated with contaminant, desiccants are ineffective to absorb moisture. Regeneration thereof is then required.
A prior art method for regenerating granular desiccants consists of immersing the contaminated desiccative material into baths of solvent. Of course, the solvent is selected in function of the contaminant or contaminants involved. Repeated baths may be required to dislodge the contaminant(s), the desiccant being dried after each bath. Another drawback of this prior art method is that the solvent itself has to be recycled and the sludge disposed of.
When the contaminant is formed of simple molecules, a bath containing a compound reacting with those molecules while dislodging them from the desiccant can be used. It is also possible that the contaminant be dislodged in water baths, when water is more easily absorbed by the desiccant than the contaminant.
When the contaminant(s) are volatile or have a low temperature of evaporation, another prior art method consists of using a kiln or furnace to heat the desiccative material to thereby evaporate the contaminant(s). The gaseous emanations must then be analyzed to determine whether they have to be recovered and destroyed, or they can be released into the atmosphere.
U.S. Pat. No. 5,086,716 granted to Lafser, Jr. on Feb. 11, 1992, proposes a rotary kiln for disposing of solid waste and recovering a portion of the energy and materials value of the waste. The kiln includes an inclined, cylindrical vessel having a higher end supplied with waste material. A burner is installed at the lower end of the cylindrical vessel to heat gases in the interior of that vessel and thereby process the waste material moving from the higher end to the lower end of the inclined vessel. Accordingly, the temperature progressively increases from the lower end to the higher end of the cylindrical vessel. The kiln of U.S. Pat. No. 5,086,716 presents the two following drawbacks:
the kiln of U.S. Pat. No. 5,086,716 exposes partially the particles of waste material to the flame of the burner, produces a temperature which is not constant along the cylindrical vessel and continuously moves the waste material along the cylindrical vessel whereby the waste material is not processed uniformly; and PA1 the energy consumption is increased by the position of the burner above the material to be processed; heat raises in the upper portion of the cylindrical vessel of the kiln where there is no material to be processed and is evacuated through the higher end of the vessel.